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PARKER: THE REACTIONS OF METRIDIUM. 1s 
side of the elongated mouth, and two very pronounced grooves, the 
siphonoglyphes, one at either end of the mouth. Not unfrequently, 
as McMurrich (91, p. 131) has already observed, only one siphono- 
glyphe is present ; occasionally three can be observed, in which case 
the mouth is more or less triangular in outline, instead of forming a 
slit with approximately parallel sides. 
As is well known, each siphonoglyphe is an open ciliated groove, by 
which a current of water passes into the gastrovascular cavity of the 
actinian. I was unable to check or reverse this current so long as the 
animal remained expanded, and any small body caught in it was certain 
to be carried inward. The animals upon which I experimented took 
in through their siphonoglyphes, with apparent indifference, carmine, 
India ink, particles of India-rubber, sand, sugar crystals, small pieces 
of meat, paper pellets, meat juice, solutions of quinine, sugar, and even 
picric acid ; in the latter case to such an extent as to kill the ciliated 
cells lining the siphonoglyphe, and thus stop the current. It is possible 
that some muscular movements of the gullet, seen when the siphono- 
glyphes contained meat or meat juice and not observed at other times, 
may have been due to a chemical stimulation of the siphonoglyphe sur- 
faces ; but, as I was unable to control the meat juice so as to be sure 
that none of it reached the lips by diffusion, I am not certain whether 
this response may not have been the result of accidental stimulation of 
the lips. 
As can be demonstrated by the use of carmine, the whole surface of 
the furrowed swollen lip is ciliated. When the lips are gently flooded 
with carmine, this substance is swept outward, and, after passing slowly 
over the intermediate zone, is discharged from the oral disk by the ten- 
tacles. The movement is uniform over the whole surface of the lips, and 
is as characteristic of the ridges as of the grooves between them. This 
outward current seems to be the usual one for the lips, and must be re- 
garded as the complement of the inward current in the siphonoglyphes. 
When, however, a piece of meat is placed on the lips, instead of being 
swept outward as the carmine was, it is carried inward and passes down 
the gullet, in part by peristaltic movements and in part by ciliary action. 
These reactions are due to the chemical stimulation of the lips and 
gullet by the soluble constituents of the meat, and are not the result 
of mechanical stimulation, as can be demonstrated by applying filtered 
meat juice to the lips, in which case the whole reaction follows, though 
no solid material is swallowed. 
The peristaltic movements of the gullet are plainly muscular responses 
